1. Field of the Invention
The present invention relates to a control apparatus including a joystick for controlling a control target, a control method, and an ophthalmologic apparatus including the control apparatus to electrically perform vertical movement of an optical system as the control target, for imaging and measurement of an eye to be inspected.
2. Description of the Related Art
As a configuration for controlling a control target with a joystick, a fundus camera including a joystick to control an optical system may be taken as an example. In a conventional ophthalmologic apparatus such as the fundus camera, the joystick is used for positional alignment between the optical system of the apparatus and an eye to be inspected. In such an apparatus, the joystick is inclined to perform back-and-forth movement and lateral movement, while the joystick is rotated to perform vertical movement. More specifically, there are known an apparatus in which the optical system is vertically moved manually by rotating a feed screw of a vertical movement drive mechanism of the optical system in combination with a belt, a gear, and the like, and an apparatus in which the optical system is vertically moved electrically. As the apparatus in which the optical system is vertically moved electrically, there is known an apparatus in which a motor is controlled so that the optical system is moved at a speed proportional to a rotation speed of the joystick (see Japanese Patent Application Laid-Open No. H05-317250). Further, there is known an apparatus in which the motor is controlled so that the optical system is moved at a speed nonlinear with respect to the rotation speed of the joystick, and as the joystick is rotated more quickly, the optical system can be moved at higher speed (see Japanese Patent No. 3,237,907).
However, in each of the apparatuses described in Japanese Patent Application Laid-Open No. H05-317250 and Japanese Patent No. 3,237,907, the rotation speed of the motor has an upper limit, and hence, when the rotation speed of the joystick becomes a fixed value or larger, the moving speed reaches to the upper limit though the joystick is rotated even quickly. Therefore, there arises a problem that the moving amount conversely decreases when the joystick is rotated quickly. There is a method in which a motor having a higher upper limit of the rotation speed is employed to control the motor to track the rotation speed of the joystick, but in this case, the high-performance motor is generally large in size and expensive. Further, a high-output power source is necessary to drive the motor, resulting in a problem that the apparatus becomes expensive and large in size.